This invention relates to a substantially planar diaphragm and supporting frame assembly for use in an electroacoustic transducer and more particularly the diaphragm uses, in principle, the teaching of my U.S. Pat. No. 4,003,449. The diaphragm disclosed in said specification has been further developed in an effort to improve the quality of the sound when such diaphragm is used in a so called "flat loudspeaker". Tests have shown that the marginal portion of the diaphragm should be so supported on a frame that the active portion of the diaphragm may almost be considered as being floatingly supported, whereby the sound qualities become improved.